The MSI PRO B660M-G keeps expansion simple — one PCIe 4.0 x16 and one x1 slot

A single PCIe 4.0 x16 slot for your GPU and one PCIe 3.0 x1 for a modest expansion card — nothing fancy, but that’s what you expect from a micro-ATX board at this price tier. The x16 slot runs at full Gen 4 bandwidth, so even a modern graphics card won’t be bottlenecked.